This is a novel about philosophy. Yet, like Will Hutton’s book on the British economy, The State We’re In, it is in the best selling non-fiction lists.

The form the novel takes is the story of two teenage girls, one getting letters about the history of ideas from a mysterious middle aged man, the other with a father serving as an officer in a United Nations force in the Lebanon.

But the storyline is mostly a pretext for expounding the successive stages philosophy has gone through in the last 2,500 years. Chapter by chapter the girls are introduced to the questions philosophers from Heraclitus to Sartre have asked – ‘How can we have certain knowledge of the external world?’, ‘What is the connection between mind and matter?’, ‘How do we decide what is good and bad?’, and so on – and the successive answers they gave.

In the process there are fairly uncomplicated explanations of terms like ‘idealism’, ‘atomism’, ‘materialism’, ‘empiricism’, ‘rationalism’, ‘dialectics’ and ‘existentialism’. Such terms are usually presented as a dry list of definitions to be learnt. Here, by contrast, they are introduced in the context of dealing with the problems which anyone encounters in trying to come to grips with the world around us.

That is why many people with little previous knowledge of philosophy have picked it up and read it avidly. It has opened to them a world of ideas from which they were previously excluded.

There are faults with the book. A quick tour of any ideas is bound to treat some superficially and to distort others.

More importantly, the author tends to present the history of ideas and cultures as having a life of its own. But in reality people develop their ideas in response to problems which arise as they try to come to terms with them in practice as well as in theory. The great philosophers were people who were best able to express the confusions felt by wide social groups at particular historical moments. If you don’t grasp this, you cannot understand why, for instance, the question of how we can have certain knowledge arose whenever a particular form of society entered into great crisis – first in Ancient Greece, then in 17th and 18th century Europe, and finally throughout the world in the mid and late 20th century.

Marx famously insisted that ‘philosophers have interpreted the world in many ways, the point is to change it’. By this he meant that only by dealing with the wider social crisis can we come to terms with the uncertainty of ideas in the society around us.

But this is not the same as saying the history of philosophy is irrelevant. It is about how people questioned things which had previously been taken for granted, asking questions rather than simply repeating, parrot fashion, what they had been taught. It is about having a critical approach to the existing world and existing ideologies.

That is why Marx’s own materialist dialectic builds upon the insights of successive generations of philosophers while showing their inadequacy.

Sophie’s World won’t tell you all this (the section on Marx gives only a brief account of his ideas and makes the mistake of presenting Stalin and Mao as his 20th century heirs). But it will provide you with some of the background knowledge you need better to understand some of the more ‘philosophical’ writings of Marx, Engels, Lenin, Trotsky, Gramsci and Lukacs.